Traditional artificial lift methods, such as the sucker rod system, have proven to be extremely inefficient and uneconomical in evacuating oil from low or marginally-producing wells. This problem is aggravated by the fact that a very high percentage of the producing oil wells in the United States fall into the low or marginally producing category.
Furthermore, sucker rod systems may cost as much as $100,000 and may have power requirements necessary to operate 10 or 40 horsepower motors. In addition, such systems are unable to remove sand, paraffin, and other non-petroleum solids from the well. These elements eventually prevent further oil production resulting in the shut-down of the well for two to three days for reworking. Obviously, such a shut down results in a significant loss of revenue to the oil well owner or leaseholder because of the cessation of oil flow. A large portion of this lost time is due to the time and labor necessary to remove the sucker rod system for reworking the well, and then replacing it.
Improved oil well evacuation systems have proven to be very efficient and economical in low and marginally producing oil wells. In the system disclosed in the above-referenced related application, an evacuation system utilizing an endless belt apparatus and method for accomplishing artificial lift are disclosed.
The endless belt is flexible and is driven between a well head station at the surface of the ground and a down hole module located near the bottom of the well. The belt carries transport units or cups which efficiently evacuate oil, water, sand, and other oil production by-products from the well as the belt is power-driven down to a level near the bottom of the well, through the down hole module and then returned to the well head station. The well head station comprises generally a container supported by a frame which is mounted near ground level on the well head. The station includes a motor and sprocket system for driving the endless belt through the course just described.
Also comprising the well head station are a number of apparatus designed to remove oil and other by-products from the inside and outside of the transport units and belt. The down hole module is located near the bottom of the well and serves as a turn-around station for the endless belt. It also assists in the excavation of the oil well.
Since the oil production may be at depths as low as 2,000 feet, the weight of the belt itself, in an endless belt system, is a significant factor to contend with. While the belt is completely joined in the endless configuration, the weight on one side of the belt, that is going down into the well, is balanced by the other side of the belt which is emerging from the well. For convenience, these two portions of the belt can be referred to as the "entrance side" and "exit side," respectively, of the endless belt. However, as soon as the endless belt is broken, for example in order to initially install the evacuation system in the well, or to modify it in any way, then this balance is lost. Furthermore, while in the balanced condition, very little power is necessary to drive the endless belt. Obviously, when the endless belt is broken, either in the installation or modification of the system, each of the broken ends must be securely held to prevent the weight of either side of the belt from causing it to fall to the bottom of the well by force of gravity.
Producing oil wells are frequently found in remote locations which are difficult to reach. The terrain surrounding the oil well may be hilly or rough, further complicating the servicing of the oil well evacuation systems.
Thus, a need has arisen for facilitating the installation and modification of such endless belt systems, and for improving their performance.